IF/OR/AND statements with multiple input with multiple output calculations

I have the below spreadsheet, where C8 can be one of fourteen values.

I have three different formulas that will be calculated in H8 depending on the value in C8, G8, with either D8,E8, or F8. Where using cells D8,E8, or F8 in calculation will depend on value in C8.

I have constructed the three separate equations below which work by themselves. I was wondering how do I string them together in one IF/OR/AND statement?

Second question how do i keep H8 to stay blank until all three cells (C8, G8, with either D8,E8, or F8) for each formula is filled out.

Equation for 0.5 =IF(OR(C8=0.5),(100-(((D8-56)*5)+(G8*1))),"")

Equation for 0.55 =IF(OR(C8=0.55),(100-(((E8-102)*5)+(G8*1))),"")

Equation for values 0.6,0.7,0.75,1.0,1.0625,1.125,1.1875,1.25,1.325,1.375,1.4375,1.5

=IF(OR(C8=0.6,0.7,0.75,1,1.0625,1.125,1.1875,1.25,1.325,1.375,1.4375,1.5),(100-(((F8-108)*5)+(G8*1))),"")